As of September 30, six cases of tuberculosis (TB) and an
additional 53 persons with significant reactions* to the tuberculin
skin test have been identified in an outbreak of TB in California,
Montana, Nevada, and Utah.

In November 1982, a 19-month-old child in Missoula, Montana,
was
diagnosed as having TB based on hilar adenopathy on chest
radiograph
and a significant tuberculin skin test reaction. The child's only
known contact with a person having a history of TB was with a
30-year-old woman who was a close family friend and the child's
babysitter.

The woman submitted to diagnostic evaluation in February 1983.
Her chest film showed a 5-cm right apical cavity. A sputum culture
yielded Mycobacterium tuberculosis; 50% of the organisms were
resistant to isoniazid (INH). Subsequently, this patient's husband
was found to have a large lesion in the right pleura and was
sputum-culture positive for M. tuberculosis sensitive to INH. M.
tuberculosis isolates from both the woman and her husband were
identified as phage type 2 (7, 12, 13).

The woman had many social contacts. Besides working as a
babysitter and having part-time jobs that brought her into frequent
contact with the public, she was extremely active in a variety of
church, community, and school activities. As part of the
investigation, over 1,000 persons have been skin tested in Montana.
These include over 200 persons who had identifiable contact with
the
woman, as well as over 500 persons who belonged to groups
potentially
exposed to her.

Three other cases were identified. All were in children 3-4
years
of age who had significant tuberculin skin test reactions and
pulmonary infiltrates and/or respiratory symptoms. For these three
cases, the exposure to the woman was either through babysitting or
family visits. All patients are being treated with multiple drugs
to
which the INH-resistant organisms are susceptible.

To date, 37 reactors (persons with significant tuberculin skin
test reactions) have been identified in Montana. Of these, 31 had
identifiable contact with the 30-year-old woman. The remaining six
reactors had contact with the other cases. All reactors are taking
rifampin as preventive therapy. Nine other reactors in Nevada and
Utah and one reactor in California have been identified, all among
relatives and friends of the woman. Contacts have also been
identified in Illinois, Oklahoma, Washington, and Wyoming; to date
none of these contacts who have been skin tested have shown a
significant reaction.

Investigation of the woman's medical history revealed that in
January 1979 in Nevada, she had been diagnosed as having TB; at the
time, she had a 3-cm right apical cavity and a sputum culture that
yielded M. tuberculosis sensitive to INH. She was treated with INH
and ethambutol. After diagnosis of her illness, an additional 11
persons in Utah and Nevada were identified as having significant
tuberculin skin test reactions; all reactors were relatives or
friends
of the woman. Eight months after diagnosis, she moved to Missoula,
Montana, with a 3-month supply of medicine. However, she did not
complete her course of treatment.

Of the six cases in the outbreak, four patients (67%) are under
15
years of age. Of the 53 reactors who have also been identified, 25
(47%) are under 15 years of age. Thus, nearly half (29/59) of the
infected persons are children.

Editorial Note

Editorial Note: This outbreak has several important facets. The
first is that of drug resistance. While it is difficult to
pinpoint
the reason why INH resistance developed in the woman presumed to be
the source of infection, probably the most important factor was
that
the patient failed to complete her treatment. Patients being
treated
for TB should be carefully monitored for compliance until the
recommended course of therapy is completed.

Of note was the fact that both the woman and her husband had
the
same M. tuberculosis phage type, while only the woman had
INH-resistant organisms. Her husband may have been infected before
her organisms became resistant. Although only the woman has
bacteriologically confirmed INH-resistant TB, there is a high
probability that the four children with TB were infected with
INH-resistant organisms. Therefore, they were placed on therapy
with
a combination of drugs to which the INH-resistant organisms are
sensitive.

Since there is also a relatively high probability that reactors
without disease have been infected with INH-resistant organisms,
these
individuals have been given rifampin as preventive therapy.
Although
the efficacy of preventive therapy with rifampin has not been
demonstrated in controlled trials, the results of a study using the
Delphi technique and decision analysis to determine the choice of
preventive treatment for INH-resistant tuberculous infection
support
the use of rifampin (2). This outbreak is the largest in which
rifampin has been used as an alternative regimen to prevent TB.

Another notable aspect of this outbreak is the large number of
infected children, including four with TB and 25 reactors. This
illustrates that TB in children is still a problem in this country.

A final aspect of this outbreak is the interstate transmission
of
tuberculous infection. Infected persons have been identified in
four
states; contacts have been identified in eight. Since transmission
occurred across state lines, efficient communication between local,
state, regional, and federal health authorities has been an
essential
part of efforts to control the outbreak.

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